Publication no. C-2002-0801-05R |  VIEW ARTICLE

Separation and Characterization of Barley Starch Polymers by a Flow Field-Flow Fractionation Technique in Combination with Multiangle Light Scattering and Differential Refractive Index Detection.

S. You (1), S. G. Stevenson (2), M. S. Izydorczyk (2,3), and K. R. Preston (2). (1) Dept. of Food Science, University of Manitoba, Winnipeg, MB R3T 2N2, Canada. (2) Grain Research Laboratory, 1404-303 Main Street, Winnipeg, MB R3C 3G8, Canada. Contribution 829 of the Grain Research Laboratory. (3) Corresponding author. E-mail: <mizydorczyk@grainscanada.gc.ca> Phone: 204-983-1300. Cereal Chem. 79(5):624-630. Accepted April 19, 2002. Copyright 2002 American Association of Cereal Chemists, Inc.

Flow field-flow fractionation (flow FFF) with frit inlet and frit outlet mode (FIFO) was coupled online to multiangle light scattering (MALS) and refractive index (RI) detectors to investigate the molecular characteristics of normal and zero amylose barley starch polymers. Application of two different cross-flows, 0.35 mL/min followed by 0.1 mL/min, and constant channel and frit flows of 0.1 and 1.0 mL/min, respectively, permitted a complete separation of amylose and amylopectin. The improved signals from the detectors due to application of the FIFO mode enabled the proper characterization of the small molecular weight species, as well as significantly enhanced the reproducibility of the measurements. The weight-average molecular weight (M(w)) and z-average root-mean-square (RMS) radii of gyration (R(g)) values for amylose and amylopectin in the normal starch samples were 2.3 × 10(^6) and 280 × 10(^6), and 107 and 260 nm, respectively. The M(w) and R(g) of amylopectin in the zero amylose starch samples were 360 × 10(^6) and 267 nm, respectively. The slopes (alpha) obtained by plotting log M(w) versus log R(g) for amylose and amylopectin were 0.6 and 0.3, respectively. These results are in good agreement with the theoretical prediction of the molecular conformation of amylose and amylopectin.